drm: use drmIoctl everywhere

Well just core drm. All the other callers in there that still use
direct calls to ioctl have some custom retry logic already, so should
be good already.

All the other offenders (tests, freedreno/kgsl, ...) don't really
matter (e.g. kgsl is the blob library and so not a drm thing) or are
again special exceptions with their own retry loops.

Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>